Variable speed friction gearing



Feb. 12, 1935. J. H. RoBER'i'soN Er AL 1,990,614

VARIABLE SPEED FRICTION GARING Filed Aug. 20, 1931 4 Sheets-Sheet l Feb. l2, l1935. J. H. ROBERTSON Er Al.

VARIABLE SPEED FRICTION GEARING Filed Aug. 2o, 1951 4 Sheng-sheet 2 Feb 12, 1935. J. H. RoBER-rsoN E-rAL 1,990,614

' VARIABLE SPEED FRICTION GEARING Filed Aug. 2o,- 19:51 4 As1we1;f.-,-shee 5 Feb. v12, 1935. J. H. ROBERTSON Er AL 1,990,614

I VARIABLE SPEED FRICTION GEARING' I Filed Aug. 20, 1931 4 sheets-sheet 4 fag-9.6]

Patented Feb. 12, 1935 Lenen :PATENT oFF-ica Y 1,990,614 vARIABLE SPEED Farorroiv .eEARINd YJohn Hogg Robertson, `John Robertson, Jr., Leonard 'Gutteridgd and Lionel.Horacellow ard, London, England `limitation August 2o, 1931, serial'nnttassg In Great Britain February 21, 1931 V2 claims. (o1. 741-199) This invention relates to variable'friction gearing of the type in which a driven member is adapted to make face` contactk with a driving extent so that-,contact takesplace at points (or limitedareas) -of which the respective -radial dise tances frornthe axes Aof themtwo members are Y unequal.

driven.memberrconsisting of a Wheel or disc ,with

Y invention.

The present jinvention consists in .improved ,arf lrangementsfor obtaining and controllingthe engagernent of the drive, .the variation of the transmissionratio, and the .pressure which maintains the two members in frictional engagement during operation.

The invention comprises the use'of a 4friction clutchl conveying the drive ,tothe friction gear'- ving members, for the purpseof relieving the lattenof wear due to slip aft-starting ando-ther times, in combination with means forregulating the engaging 'pressure of the friction .gearing membersfso as .to ensure thatslip atthe surfaces of the latter is avoided vasfar-asy possible. In theimproved variable speed friction gearing, the driving member, consisting of a conical disc, is mounted upona shaft to which the drive can be communicated through a friction clutch, which may be automaticallycontrolled by a centrifugal governor, andthelaterally displaceable an 4,annular friction face isregulated asreg'ards its coaxial orveccentric position by ag'ear-con trolling device WhileV being vpressed, axially forwardA into engagement with the driving member by a second or pressure-controllingdevice. The.

gear-controlling device may be operated by power independent ofthe friction gearing, for example by fluid pressure, andthe second or pressurecontrolling device by which the drivenmember is pressed :axially forward into engagement, may

be operated by thevrtorque upon the `-sh'aftof said4 drivenY member. Y A v The invention is Vhereafter described with referenceto the accompanying drawings inwhichz Figure `1 isa sectional'elevation Aofla, l,variable speed friction gearing embodying thepresent Figure. 2 is an end elevation seen from the right of Figure 1.V v-

VFigures 3 and flare details of the'controlling mechanism for the automatic friction clutch V seeninlgure 1. j

plingbetweenthe ydriven member and the transl mission'shaft. Y c

'Figure' f6 ,is `a sectional .View of the oil pump for the hydraulic operationA of .the gear.

,j lFigure 7 is a sectional view of theY control valve for the hydraulic ram. r

`Figures8 and 9 are diagrams showing the control valve ,i'n two other-positions.

Figure `lOis a diagram showing the friction clutchV provided with hydraulic control.

Inthe following descriptionit will be assumed that the present invention is applied to a motor vehicle, though it will be clear thatthe invention mayv be applied to other .purposes and to machinery in general. v t.

Referring to Figure 1, the flywheel 1rv secured upon the crankshaft Vof'the engine is provided with a friction clutch, of which the driven member b is carried'by a flanged hub b1 upon a shaft c'rotatablymounted inside'the bell housing or cover cg'of the'flywheelpit. The friction clutch may be operated for disconnecting the drive, by apedal orQother control of any suitable type, by means of .the cross shaft d carrying a fork d1 engaging a -slidable thrust bearing orcollar d2 mounted. aroundthe inner vend of the central boss-cflof the-,cover c?. The thrust collar d2 acts upon the inner endsof a number of clutch levers a1 fulcrurned at'az'upon the cover plate bzgof the clutch, the outer .ends of these levers being pivotally connectedV by pins ato slidable plungers a4 passing through the cover plate b2 and*V engaging the presserplate a5.

.The engagement of the .friction clutch plates a, b, 5,instead of being produced by a spring or springs inV theusual manner, is obtained'by the action of a speed-responsive governor mechanism (see Figure 3) which as soon as the engine f exceeds a low .idling speed, and provided vthe Vclutch isinot disengagedby the pedal or the like causingLthe plungers aV4 to draw the presser plate d5v away'from the driven plate` b, tends to bring applied to the clutch, yielding connections such as coiled springs V65,01a rubber buffers are interclutch. Ylin order toA limit the engaging pressure posed between the lever bosses and the clutch presser plate a5, these connections becoming fully loaded at completion of the outward movement of the governor levers e, which takes place at a moderate speed of the engine. As shown for example in Figure 4, the extension of the springs e5 may be limited by adjustable stops e3 carried by rods e4 passing through the studs e1, Vthese stops coming into operation during the automatic release of the clutch due to decrease of the engine speed, so as to relieve the presser plate a5 of the spring pressure while the springs still remain under compression; conversely, during the automatic engagement of the friction clutch, the pressure will be applied by the governor levers e acting through the springs e5 under an initial compression determined by the adjustment of the stops e3. t

The driving disc f of the friction gearing, consisting for example of a plain steel cone, is shown secured by keying upon the tapered end f1 of a sleeve f2 surrounding the clutch shaft c, the sleeve being connected through the shaft c to the driven member b of the clutch by splines or the like floating connectionl b3 to permit the disengaging movement of the` clutch member b, while the sleeve itself has substantially no axial travel beyond that requiredfor the freedom of its bearings c1 which are supported in the bell housing cover c3; the latter is stiffened by ribs or the like so as to withstand the end thrust received through the bearing c1 behind the driving disc and generated by the pressure of the driven member g against said disc.

The driven member g, which is displaceable both axially and laterally; is fitted with a bevelfaced friction ring g1, made for example of an asbestos or like. compound in combination with a synthetic Vresinous or other binder, the ring being held by rivets or bolts g2 in a wheel or spider g3 made of aluminium alloy, pressedsteel or the like, h-aving a flanged or channel rim g4. The driven shaft h, formed with a flange h1 supporting the driven member secured thereon by studs h2, is rotatably and slidably mounted in a sleeve h3 within a cylindrical socket h4, a screw coupling device being interposed between the slidably mounted shaft h which is formed with quick-pitch screw threads i and the sleeve h3 formed with female threads i1; this sleeve is shown integral with the primary shaft of a change-speed and reverse-gear box from whichthe socket h4 extends.

InV proportion to the torsional resistance to motion of the primary or transmission shaft and sleeve h3, the screw coupling device i i1 produces an axial thrust along the slidably mounted shaft h so as to forcevthe driven member g into frictional contact with the driving disc f, the re@- action of this thrust being taken by a ball or other bearing i2 inside the gear box.

Figure 5 illustrates a coupling device which may be substituted Vfor the screw coupling i 'il between the shaft h. secured to the driven member g and the sleeve h3 which `forms the primary shaft of the transmission. In this modication, the shaft h is fitted with a transverse pin j the ends of which engage in helical slots j formed in the surrounding sleeve h3, the inclination andv direction of these slots being the same as those of the screw-threads i i1 in the coupling shown in Figure -l.

The gear box and socket h4 are mounted to rise and fall upon a pair of parallel slide rods lc (see Figure 2), the position of the socket being controlled by movement in either direction as desired, by means of a hydraulic ram k1, the piston k2 of which is secured to the socket by rod ko. The slide rods k are shown as being set in parallel vertical planes at an inclination (see Figure l) substantially equal to that of the lowest radius of the driving cone J', but obviously the slide rods may be set at a different angle of inclination or even vertically, so that the lateral displacement of the gear box and socket h4 will cause axial travel of the driven member g and shaft h in relation to the socket h4.

The ram cylinder is carried by a beam k3 supported by brackets Ic4 upon the housing R5, the ends of the beam forming attachments for the lower extremities of the guide rods k, the upper extremities of which are connected by an arched bridge-piece k6 having its ends likewise supported by brackets h4 at the top of the housing h5.' As seen in Figure 2, the `slide rods Ic pass throughrinclined lugs h5 upon the opposite sides of the socket h4.

The movement of the hydraulic ram piston for raising or lowering the gear box and socket h4 and thereby varying the transmissionrratio of the friction gearing, may be initiated, stopped or reversed by the driver of the vehicle, for example by one or more control valves placed -at any convenient position and controlled from the steering wheel or otherwise, in order to produce movement in either direction as desired. Thus the transmission gear may be selected or changed to suit variation of driving conditions byV bringing about a movement ofthe socket h4, the friction gearing members f g being maintained in constant engagement by the screw coupling device i i1 which, so long as the torsional resistance continues, causes an axial thrust upon the driven member g in proportion to such resistance.

In the arrangement illustrated in Figures 6 and '7, hydraulic pressure employed for the gear controlling device is generated by a small reciprocating pump l, having its piston l1 driven by an eccentric l2 upon the crankshaft of the engine, the pump suction and delivery being connected by pipes l3 I4 respectively to the engine sump and to the casing m of a controlling piston valve n; the oil entering the casing m acts upon a pressure relief Valve m1 controlled by springs m2 m3 and slidable over a port m4 allowing the oil to escape into the sump when a given pressure is exceeded.

Figure '7 shows the control valve casing m located inside the engine sump or crank case m5, so that any leakage of oil from lower end of the valve n is confined to theinterior of the crank case. The valve casing is formed with an annular admission port n1 receiving oil from the top of the relief valve m1, Awith two ports n2 n3 delivering through pipes n6 11.rl respectively to the top and bottom ends of the ram k1, and with two ports n4 n5 allowing the oil to escape into the sump. The piston valve n is formed with three circumferential grooves n ng n0, cooperating with the ports 11,1 11.5 in the lwall of its casing, and its movements are limited by abutments shown in the form of screw caps enclosing the springs which normally keep it in the middle position, as shown in Figure 7. In the normal position, the port 'n3 is shut off, so that the ram piston k2 is prevented'from falling either under the weight of the parts connected thereto or by the centering effect of the axial pressure between the members f and g, while the pump delivers freely to exhaust through the ports al am# which"arefconnectdby the grooves ns' 119. Upon `sliding movement' of Vthe piston valve-n `in'eitherdirection,]as shown in Figures iii-and Q-respectively, the `oil pressure is directed by the groove ng andthe port n2 or vn3 toone or other end of Ithe iamv k1, the other end of which connected tol-exhaust through theports 'n3 n (connected by the groove nlll'or the 'ports n2 114 (connected by the groove 11,9), sothat downward or upward movement of the socket h4 and of the driven member'g ywillfbe produced The piston valve casing m may be .located ad-Y jacent tothe ram 'lcas shown in Figure 7, and the valve spindle connected at o1 to one end of a rocking lever o, the other end-of which is connected at o2 tothe pistonl rod la or tosome part moving with the` latter, while an intermediate'point o3fof'the llever' is operated by the manual orlilre control :device "p through arbell crank p1 and links p2 py'the relative lengths of the two arms of the-lever o are made proportional tothe respectivestrokes of the piston valve n andof the rampiston 102, so that the r-amis caused to follow themovement of the' control device p; as indicated in chaink lines in Figure '7. The movement of the rocking lever o produced by thepiston rodlco will then tend to center thepiston Vvalve n in its normal position,

tuy

Cil

stopping the `moverment of the socket hf at a position depending upon the setting of the manual control device p, and thepiston valve being centered by its springs. Y

The Ahydraulic ram k1 may be made singleacting, forexample so as to lift the driven member towards the low gear positionand to prevent its fall towards' the direct drive position, the control valve n being modified accordingly by the omission of the port n2, the groove 11,9 andthe pipe connection n. LikewiseY the arrangement shown in Figures 1 and 2 may be altered so that the low gear is obtained in the bottom position.

in addition to the axial thrust resulting from the torsional resistance on the transmission shaft, a light initial engaging pressure upon the driven member g is produced by a spring 1' enclosed in the slidable driven shaft h and compressed between a screw plug r1 at the outer end and a washer r2 supported by a thrust rod r3 bearing upon a steel ball r4 at the forward end of the nal drive shaft s of the gear box, the thrust being taken upon the rear bearing of the shaft s.

A slidable gear wheel s1 mounted on splines upon the shaft s is formed with clutch dogs s2 for engaging corresponding dogs at the rear end of the sleeve h3 which forms the primary shaft of the gear box, this sleeve carrying a constant mesh pinion h6 driving a gear wheel'LL upon the Vsleeve t1 which forms the layshaft of the' gear box. When the clutch dogs s2 are engaged with the sleeve h3, the gear box provides a direct drive to the shaft o; in the position shown in Yliigure 1, the gear box is in neutral; by sliding the gear wheel s1 towards the right, by means of the striking forks s3 operated by an external lever s4, the wheel slcan be brought into mesh with a pinion t2 on the layshaft, giving a low-gear drive Yto the shaft `@,ithis being intended for example for use in starting or under emergency conditions when a greater reduction of speed or a lowergear ratio is required than can be obtained by the friction gear- 'ng alone. Finally a reverse drive can be obtained by sliding the gear wheel s1 further towards Vthe right, so as to mesh it with an idler wheel (not shown) driven by the reverse pinion 't3 on the lays-haft.

It will be noted that the engaging pressure upon vtheiriction members f g remains proportional to the torsional resistance to motion of the sleeve h3, neglecting the eifect of the spring r, and that the useoi' the emergency low gear or of the reverse drive provided bythe gear box does not affect the relative conditions of operation of the coupling device z' il or'y 7'1 and the friction members f g.

Moreover an automatic free-wheeling action is provided by the screw or cam coupling device i'z'l or y' 7'1 sinceany tendency of the vehicle to overrun the engine will result in the drivenmember 'g being relieved of axial thrust, owing to the reversal of the torque in the transmission. When this occurs, the screw or cam coupling device will tend to draw back they shaft hagainst the action of the spring 1^, but without actually separating the members f and y, until a state of balance is reached at the point where the driven member g slips upon the slower running member f under a lightcontact pressure (less than the'compression of the spring r) theiresistance thus set up in the transmission being just sufiicient to maintain the reversed torque required for causing the screwcoupling device to oppose the spring. This spring r being intended mainly to secure an initial engagement of the gearing# members, when the vehicle is being started 'from rest, the full compression of the spring is relatively we'al`;" consequently when this spring compression is op- 1 posed by the reversed action of 'the screwcoupling device, the differential pressure at thefsurfaces the pressure being increased .to normal as soon as the engine resumes the drive so as to produce a torque in the forward direction at the screw or cam coupling device i il or i il.

Hydraulic or other pressure may also be employed for producing the axial pressure which maintains the friction gearing members in engagement, by means for example of a ram mounted upon or connected to the shaft oi the driven member inside the sleeve h3, the pressure acting at any given time being regulated manually or by any convenient means.

Similarly, the friction clutch may be controlled by the hydraulic pressure, for example as shown in Figure 10; the oil pressure from the pump Z is admitted through a suitable valve u to a ram o of which the piston 'U1 is connected to the pedal lever'o3 upon the cross shaft d, the hydraulic pressure acting preferably to release the' clutch against the action of clutch springs c4 fitted bretween the presser plate a5 and the cover plate b2, through the medium of the thrust collar cl2, levers a1 and plungers a4; in the re-engaging movement, the ram o will act in the manner of a dash pot to prevent sudden clutching effects. Y

It will be understood that the invention is not vlimited to the particular arrangement and dethrough the socket on the radius arm, the screw or cam coupling device Yi i1 or j il causing or allowing an axial displacement of the driven member g in proportion to its lateral displacement, or alternatively the radius arm itself may be given an axial displacement along its pivot, proportional to its swinging movement, by means of a quick pitch screw or cam device, so as in either` case to maintain constant engagement of the driven member g with the coned driving member f, while the coupling i 121 or y' i1 produces an axial thrust on the driven member g in proportion to the torsional resistance as above described.

The swinging movement of the radius arm may be controlled bya toothed quadrant in mesh with an irreversible vvormk rotatable in either direction by a suitable motor, or there may be employed a hydraulic cylinder the piston of which acts directly upon the radius arm or upon a crank secured thereto, the pressure and exhaust valves being so arranged that the radius arm will remain in any selected position to which it is moved by the controlling piston.

The radius arm may be replaced by a rotatable disc, the socket h4 containing the shaft and bearings of the driven member g being offset eccentrically from the axis of the disc to such an extent that on rotation of the disc the driven member can move into either the direct drive or the low gear position.

. What we claim isz- 1. In variable speed friction gearing, comprising a driving member, a driven member adapted to make coaxial face contact with said driving member, and means for displacing said driven member laterally in eccentric relation to said driving member, the combination of a coupling device transmitting torque from said driven member, said coupling device controlling the engaging pressure upon said driving and driven members both in their coaxial and in their eccentric positions according to the torque transmitted by said coupling device, and means for exerting an initial engaging pressure upon said driving and driven members, said coupling device being adapted to oppose said means for exerting an initial engaging pressure in the event of reversal of the torque at said coupling device.

2. In variable speed friction gearing, comprising a driving member, a driven member adapted to make coaxial face contact with said driving member, and means for displacing said driven member laterally in eccentric relation to said driving member, the combination of a friction clutch adapted to convey rotary motion to said driving member, speed-controlled means for engaging said friction clutch, a coupling device transmitting torque from said driven member, said coupling device producing engaging pressure upon said driving and driven members both in their coaxial and in their eccentric positions in proportion to the torque transmitted by said coupling device, and means for exerting an initial engaging pressure upon said driving and driven members, said initial engaging pressure being of low value relative to the pressure produced by said coupling device.

JOHN HOGG ROBERTSON. JOHN ROBERTSON, JUNroR. LEONARD GUTTERIDGE. LIONEL HORACE HOWARD. 

